Cancer cells exhibit alterations in parameters of nuclear architecture that control cell fate and compromise control of cell growth. Our Program has established new biological paradigms by showing that gene regulatory factors integrate cell signaling at chromatin microenvironments ('subnuclear foci') and support epigenetic mechanisms through association with mitotic chromosomes. In collaboration with other Program Project investigators. Project 1 will now establish new dimensions in gene regulation by defining perturbations in architecturally linked regulatory mechanisms during interphase and mitosis in AML and breast cancer cells. Our central hypothesis is that (i) subnuclear targeting of transcription factors to gene regulatory foci during interphase and (ii) the association of transcription factors with their target genes in mitotic chromosomes are fundamental to the retention of biological states of normal and cancer cells. Therefore, we will use IF microscopy, biochemical, genomic and proteomic approaches (i) to characterize modifications in architectural epigenetics and molecular pathological consequences of expressing the translocation-related t(8;21) AML-ETO fusion protein (Aim 1), (ii) to analyze genes that are transcriptionally and spatially controlled by Runx2 in chromatin micro-environments ('subnuclear foci') during interphase in breast cancer cells (Aim 2), and (iii) to examine Runx2 mediated architectural epigenetics in breast cancer cells by characterization of Runx2 and cognate gene regulatory factors that associate with mitotic chromosomes (Aim 3). By investigating the functional role of Runx2 in establishing chromatin micro- environments ('subnuclear foci') during interphase and architectural epigenetics in cancer cells during mitosis, we will challenge traditional biochemical views of gene regulation by defining the pathological linkages between modifications in nuclear architecture and gene expression that are fundamental to the molecular etiology of tumorigenesis.